So, I know it's very difficult to find traditional Ryukyuwan instrument like the Sanshin in USA. I too made a mistake, when I first tried to acquire it. I live in the motor city, so as you can tell, there's pretty much no Japanese community there to even look for instrument store that specializes in selling Asian musical instruments. While understanding it's very difficult to get an instrument like the sanshin without actually seeing and playing it, there's several tips I can share.
1. Do NOT, and I repeat do NOT ever try to import Asian musical instrument that is very sensitive from eBay sellers.
I've made that mistake and learned it very hard way. As usually the first place I'd look when trying to import some goods from foreign countries with decent deals is the eBay and Amazons, so I placed the order there. But really, it's better at least to import from the instrument store in Japan that actually guarantee insurance on it for 5 years or even longer depending on the instrument and where you are getting it from. eBay sellers are not usually professionals, and when it comes to things like musical instruments, the person you are buying is a typically the middle men, that really had no business/knowledge in instruments that is in question. And, when it is delivered broken, it is such a hustle to get the money back. And the fact is, the seller could be very nasty in their attitudes unlike professional instrument store person would be... especially when it comes to refunding... Also, if the seller had some kind of issues with customs in prior, your instrument will be held at custom about a month or more, before finally arriving to your home... If you live in the States that get a lot of snow storms, you'd also understand how much hustle it is to get to USPS and if you live in inner city location, your USPS service personnel may not know how to respond with claims you are trying to make with damaged/broken international shipment. I actually had to go to suburban USPS in order to get PS Form 3831 from their supervisor personnel. The first local USPS I went to, tried to convince me that I couldn't file it... And yes, it was coming from supervisor personnel at that USPS, but not all USPS supervisor persons knows the same amount of knowledge in handling international claim cases... So, anyways, it's just better to avoid unknown middle man seller on eBay, when it comes to musical instrument.
2. There are several good online stores. For my replacement sanshin that was delivered broken by an eBay seller with very nasty attitude, I decided to use Global Rakuten Market for the first time. Then, I started to search for 三線 (Sanshin) in Japanese and found 3 instruments specific sellers that I thought I'd give it a try. You can do your own research by reading reviews on the stores at Rakuten. I ordered Sanshin Case from okinawa2 (since I thought I was getting un-broken Sanshin from ebay seller at the time). I also ordered 2 water buffalo horn pick (chimi:爪 of size SS and size M), the Tiiger (ティーガー：胴巻き: body wrap for Sanshin) with blue color, shoulder strap, couple of bamboo horse (ウマ） for practicing, and the textbook with DVD as well as J-pop music books for sanshin. The okinawa2 is awesome when it comes to packing their product well. They even babble wrap the outer side of the packaging box with English notes telling the mail service person to be considerate in handling a very sensitive musical instrument! (And that was just for a case, I ordered!)
3. For global market at okinawa2, I couldn't quite find the Sanshin I like that would match my budget. The one that okinawa2 was selling for beginner was the one that usually called a "trial sanshin" in Japan, where it uses apitong wood, which wasn't really made for the instrument. I have read in different Japanese article about sanshin, where apitong wood would start to bend especially in harsh weather within a year or two... Which convinced me to upgrade the sanshin's quality a bit. For practice Sanshin, I suggest you'd look for at least made of oak tree or better Karin/Shitan wood.
4. For US buyers, you can't import the instrument that is made of real snake skin due to custom restriction. So, it's likely you are going to look for artificial snake skin for the drum part of the Sanshin. I found high grade artificial snake skin from the ChuraSaki and el-Okinawa online instrument store on Rakuten Global markets. I ended up getting the one below the link from Churasaki. I didn't order the set, since I already had bunch of stuff that I imported from okinawa2 store prior. But if you don't have anything for your sanshin, it might be better just ordering the set from the link at the bottom of this article.